The invention provides isolated nucleic acid and amino acid sequences of HsKif2x, methods of detecting HsKif2x and screening for HsKif2x modulators using biologically active HsKif2x, and kits for screening for HsKif2x modulators.
The kinesin superfamily is an extended family of related microtubule motor proteins. It can be classified into at least 8 subfamilies based on primary amino acid sequence, domain structure, velocity of movement, and cellular function. This family is exemplified by xe2x80x9ctruexe2x80x9d kinesin, which was first isolated from the axoplasm of squid, where it is believed to play a role in anterograde axonal transport of vesicles and organelles (see, e.g., Goldstein, Annu. Rev. Genet. 27:319-351 (1993)). Kinesin uses ATP to generate force and directional movement associated with microtubules.
Within this functional group of kinesins resides a group of kinesins from several organisms that share significant sequence homology, the Kin I subfamily, and that function to destabilize microtubule ends. These include H. sapiens MCAK (also known as mitotic centromere-associated kinesin or HsMCAK), X. laevis MCAK, and C. griseus MCAK.
During anaphase A, disjoined sister chromatids migrate poleward. This poleward movement is driven by kinetochores and is accompanied by the depolymerization of microtubules attached to the migrating chromatids. The kinesin MCAK plays an important role in this motility and may promote disassembly of microtubules attached to kinetochores of mitotic chromosomes.
The HsMCAK gene has a predicted 723 amino acid open reading frame, encoding a 81 kDa protein that shares 79.2% homology with hamster MCAK. HsMCAK is expressed in tissues containing dividing cells, such as thymus, testis, small intestine, colon (mucosal lining), and placenta. Genes for the Xenopus and hamster homologs of MCAK has also been cloned and characterized.
Defects in function of these proteins may result in cell cycle arrest. As such, compounds that modulate the activity of these kinesins may affect cellular proliferation. The present invention provides a novel method to identify such compounds.
The discovery of a new kinesin motor protein, and more particularly, one in the MCAK subfamily, and the polynucleotides encoding it satisfies a need in the art by providing new compositions which are useful in the diagnosis, prevention, and treatment of cancer, neurological disorders, and disorders of vesicular transport.
The present invention is based on the discovery of a new human kinesin motor protein, HsKif2x, the polynucleotide encoding HsKif2x, and the use of these compositions for the diagnosis, treatment, or prevention of cancer, neurological disorders, and disorders of vesicular transport.
In one aspect, the invention provides an isolated nucleic acid sequence encoding a kinesin superfamily motor protein, wherein the motor protein has the following properties: (i) the protein""s activity includes microtubule stimulated ATPase activity; and (ii) the protein has a sequence that has greater than 70% amino acid sequence identity to SEQ ID NO:2 or SEQ ID NO:4 as measured using a sequence comparison algorithm. In one embodiment, the protein further specifically binds to polyclonal antibodies raised against SEQ ID NO:2 or SEQ ID NO:4.
In one embodiment, the nucleic acid encodes HsKif2x or a fragment thereof. In another embodiment, the nucleic acid encodes SEQ ID NO:2 or SEQ ID NO:4. In another embodiment, the nucleic acid has a nucleotide sequence of SEQ ID NO:1 or SEQ ID NO:3.
In one aspect, the nucleic acid comprises a sequence which encodes an amino acid sequence which has greater than 70% sequence identity with SEQ ID NO:2 or SEQ ID NO:4, preferably greater than 80%, more preferably greater than 90%, more preferably greater than 95% or, in another embodiment, has 98 to 100% sequence identity with SEQ ID NO:2 or SEQ ID NO:4.
In one embodiment, the nucleic acid comprises a sequence which has greater than 55 or 60% sequence identity with SEQ ID NO:1 or SEQ ID NO:3, preferably greater than 70%, more preferably greater than 80%, more preferably greater than 90 or 95% or, in another embodiment, has 98 to 100% sequence identity with SEQ ID NO:1 or SEQ ID NO:3. In another embodiment provided herein, the nucleic acid hybridizes under stringent conditions to a nucleic acid having a sequence or complementary sequence of SEQ ID NO:1 or SEQ ID NO:3.
In another aspect, the invention provides an expression vector comprising a nucleic acid encoding a kinesin superfamily motor protein, wherein the motor protein has the following properties: (i) the protein""s activity includes microtubule stimulated ATPase activity; and (ii) the protein has a sequence that has greater than 70% amino acid sequence identity to SEQ.ID NO:2 or SEQ ID NO:4 as measured using a sequence comparison algorithm. The invention further provides a host cell transfected with the vector.
In another aspect, the invention provides an isolated kinesin superfamily motor protein, wherein the protein has one or more of the properties described above. In one embodiment, the protein specifically binds to polyclonal antibodies generated against a motor domain, tail domain or other fragment of HsKif2x. In another embodiment, the protein comprises an amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4.
In one aspect, the protein provided herein comprises an amino acid sequence which has greater than 70% sequence identity with SEQ ID NO:2 or SEQ ID NO:4, preferably greater than 80%, more preferably greater than 90%, more preferably greater than 95% or, in another embodiment, has 98 to 100% sequence identity with SEQ ID NO:2 or SEQ ID NO:4.
The invention features a substantially purified polypeptide comprising the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4 or a fragment thereof and more particularly, the motor domain of the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4 or a fragment thereof.
In one embodiment, the present invention provides a method of identifying a candidate agent as a modulator of the activity of a target protein. The method comprises adding a candidate agent to a mixture comprising a target protein which directly or indirectly produces ADP or phosphate, under conditions that normally allow the production of ADP or phosphate. The method further comprises subjecting the mixture to a reaction that uses said ADP or phosphate as a substrate under conditions that normally allow the ADP or phosphate to be utilized and determining the level of activity of the reaction as a measure of the concentration of ADP or phosphate. A change in the level between the presence and absence of the candidate agent indicates a modulator of the target protein.
The phrase xe2x80x9cuse ADP or phosphatexe2x80x9d means that the ADP or phosphate are directly acted upon by detection reagents. In one case, the ADP, for example, can be hydrolyzed or can be phosphorylated. As another example, the phosphate can be added to another compound. As used herein, in each of these cases, ADP or phosphate is acting as a substrate.
Preferably, the target protein either directly or indirectly produces ADP or phosphate and comprises a motor domain. More preferably, the target protein comprises a kinesin superfamily motor protein as described above and most preferably, the target protein comprises HsKif2x or a fragment thereof.
Also provided are modulators of the target protein including agents for the treatment of cellular proliferation, including cancer, hyperplasias, restenosis, cardiac hypertrophy, immune disorders and inflammation. The agents and compositions provided herein can be used in variety of applications which include the formulation of sprays, powders, and other compositions. Also provided herein are methods of treating cellular proliferation disorders such as cancer, hyperplasias, restenosis, cardiac hypertrophy, immune disorders and inflammation, for treating disorders associated with HsKif2x activity, and for inhibiting HsKif2x.